The proposed program of research derives from the discovery in this laboratory that at least two mutagens (active in the Ames Salmonella test, in the presence of microsomes) occur in several common commercial bacterial nutrients (e.g., Difco Bacto nutrient broth) which contain beef extract (an aqueous extract prepared by heating minced beef tissue, prepared in abbatoirs). Given that there is a significant correlation between a substance's mutagenic activity toward Salmonella and its carcinogenicity toward laboratory animals, this discovery raises a number of questions that are relevant to the incidence of cancer in people. Accordingly, the proposed program of research is designed to identify the mutagenic substances that occur in bacterial nutrients, beef extract, and similar food materials; to determine their origins (e.g., as inherent tissue constituents, or from reactions occurring in the processing of beef extract, bacterial nutrients and similar food products); and to investigate the roles of such substances in carcinogenesis. The investigations are based on mutagenic analyses, using various Salmonella strains developed by Ames, of the foregoing materials. To determine the occurrence of mutagens in these materials, dose-response curves will be obtained from extracts. To identify mutagens a series of thin-layer chromatographic fractionations will be carried out on extracts of the sample, using mutagenesis tests to locate active constituents. To determine the origins of the detected mutagens, mutagenesis screening tests will be carried out on samples obtained during commercial and laboratory preparation of beef extract and related materials, and as necessary, on various beef tissues and on materials of different age and geographic origin.